Lily Tomlin 'really plugged into' her role as a '60s radical feminist, now mother to Tina Fey's character, in the comedy 'Admission.'

Shortly before Lily Tomlin arrived on set to play an aging feminist in Paul Weitz's dramatic comedy "Admission," she had a flash of inspiration. What if she had a breastplate made to cover her upper torso, tattooed it and then appeared in the film shirtless while chopping wood? The act would perfectly symbolize '60s radical feminism.

"It seemed like a fun idea, but it was a little more than anyone could handle," Tomlin said in an interview, offering a laugh. "So I had an arm tattoo of Bella [Abzug] made instead."

That tattoo is a clever aside in the film, which opens March 8 and in which Tomlin evokes her own feminist past to play the mother of the 40-ish Portia, a romantically challenged Princeton admissions officer played by Tina Fey. From the moment the former "Laugh-In" personality appears on screen — wielding a shotgun to scare off her daughter's potential suitor — Tomlin seems to be both drafting off and subverting the stereotype of the erstwhile campus ideologue.

"As a feminist from that era, I really plugged into the role," said Tomlin, 73. "I had so many friends who were notable at the time, and then the times changed. I had an inkling of what it meant to follow a doctrine to the letter and then have it bite you on the other end."

There is plenty that's bitten about her character, who reared her daughter on her own after conceiving her in a moment of sexual liberation with an anonymous man on a New Jersey Transit commuter train. Portia still bears the scars of her mother's flippancy toward men and can't seem to make the right relationship choices. ("30 Rock" fans, take note: Michael Sheen once again plays an ill-suited Fey paramour, somehow even managing to up his unctuousness quotient.)

Portia's life is further complicated when a charming but drifter-y high-school guidance counselor (Paul Rudd) turns up with a promising student (Nat Wolff) who needs help getting into Princeton. The counselor comes bearing bombshells. The student, he says, is the son Portia gave up for adoption 18 years before, putting her in a convenient but ethically compromised position to help the child from whom she once turned away.

Though a genial comedy (written by Karen Croner) featuring likable actors, "Admission" percolates with serious themes about education, parenting and feminism. Tomlin's character has a lot to say about that last one, refusing to alter her devil-may-care attitude toward men even as she admits she may have made a mistake pushing those attitudes on her daughter.

It's a reckoning that the actress, who is also an activist for lesbian causes, says she has made in her own life.

"When you're young, you want to make a difference in the world," she said. "And you think the difference you're making is monumental, but in the overall scheme you come to realize that it's not."

A pioneer of female comedy — Tomlin was churning out stand-up albums at a time when few women did so — Tomlin says Fey is a worthy bearer of the mantle.

"Tina is sort of singular in what she creates," the actress said, adding that when she sat down to lunch with Fey on set, Fey was eager to talk about Tomlin's landmark 1980s comedies such as "Big Business" and "9 to 5." "She's a reserved, contained kind of personality, but you can just sense the intelligence."

As for seeing more Tomlin on the big screen, don't count on it. Though she's taken small TV parts — she's had a recurring role on the ABC family comedy "Malibu Country," in part, she says, because she's close with the show's star Reba McIntyre — Tomlin hasn't had a film role in four years and has no others on her docket. In that regard, at least, you can credit (or blame) her idealism.

"I can't be in a movie unless it has something that's interesting to express about the world," Tomlin said. "Or at least it can't be debasing to my view of the world."